10 - cestodes Flashcards
What is the general body plan of a tapeworm/cestodes?
A scolex (anterior attachment organ) and a strobila (a segmented oart if the body consisting of a chain of proglottids)
What is the difference between the scolex on pork tapeworm (T. Solium) and beef tapeworm (T. Saginata)
The pork tapeworm has 4 large suckers and a rostellum containing a double row of hooks, whereas the beef tape worm only has 4 suckers
Each proglottid is monoecious, what does this mean?
The proglottids contain both male and female sex organs (I.e both testes and ovaries)
What happens once a proglottid has been fertilised?
It fills with eggs and the gravid proglottid breaks off the chain and passes out in the faeces
What is the difference between the gravid proglottids of pork (T. Solium) and beef (T.saginata) tape worm?
T. Saginata has more uterine branches than T. Solium
How do cestodes get nutrients?
They absorb nutrients through a specialist transport membrane in the tegument. The tegument has microvillous projections that increase the surface area
How do cestodes excrete waste?
Cestodes have protonephridium which consists of flame cells and tubules. Cillia in the flame cells beat, which generates a current and forces water containing nitrogenous waste into the tubules. The waste the, moves out of the tubules to the external environment via excretory pores
How does a cysticercus develop?
When oncospheres obtained from the ingestion of tape worm eggs passes to tissues (via the blood) from the duodenum. The oncospheres then encysts within tissues and an embryophore (a thick membrane) surrounds the oncosphere to protect it
How is pork and beef tapeworm transmitted between humans and pigs/cows?
- eggs or gravid proglottids from an infected human are passed out in the faeces
- pigs/cows then become infected by eating vegetation that is contaminated with the egg or gravid proglottids
- oncospheres then hatch and migrate to muscle tissue where they develop cysterceri
- humans are then infected when they eat raw or undercooked meat from infected animals
What is the global distribution of taenia saginata?
Worldwide distribution, but more common in Africa, Eastern Europe, the Philippines and Latin America. It is very rare in India as Hindus don’t eat beef.
What is the global distribution of Taenia Solium?
Worldwide distribution but it’s most common in regions where humans live in close contact with pigs and eat undercooked pork. It is rare in Muslim countries as they don’t eat pork.
What symptoms do humans have when infected with taeniasis?
- mild symptoms such as abdominal pain, nausea and weight loss
- psychological distress due to passing motile segments
- in rare cases, there may be intestinal blockages
How does a human contract cysticercosis?
- ingestion of eggs through faecal contamination or
- proglottids being carried back to the stomach in reverse peristalsis
In which areas of the body can cysticercosus develop?
Muscles, eyes (rare) and the brain and spinal cord (neurocysticercosis)
What are the symptoms of neurocysticercosis?
Seizures, headaches, confusion, difficulty of balance and swell of the brain. Sudden death can occur in heavy infections
